Were you a dirty child? If so, some believe your parents did you a favor. Would you agree?

By David Martin, President & CEO of VeinInnovations

Most adults over the age of 30 remember a childhood full of dirt. People who grew up with a lot of siblings or a few pets almost certainly remember dirt. And anyone who grew up on a farm definitely would. According to the “hygiene hypothesis” your parents did your immune system a favor if they let you get grimy as a kid.

The hygiene hypothesis is back in the spotlight this week with the publication of a preliminary study from Sweden concerning kids and allergies. The study of just over 1000 children found that in homes where dishes were hand washed, kids were slightly less likely to develop allergic asthma and hay fever and were significantly less likely to develop eczema.

The hygiene hypothesis is straightforward: exposure to germs and certain infections helps kids’ immune systems develop. For years now, researchers have wondered if our first-world commitment to extreme cleanliness (antibacterial soap and surface cleaners, hand sanitizer and the like) have changed the direction of our immune response. If we’re not exposed to a diverse group of bacteria and other microorganisms as kids, do our immune systems overreact later in life?

The answer is: maybe. The dishwashing study is only observational and can’t confirm causality. Some studies have shown that children who grow up on farms are less likely to have asthma. A 2013 study found that the prevalence of asthma “…had begun to decline in some western countries, but there is little evidence that they have become less clean; Latin American countries with high infection rates have high asthma prevalence and the hygiene hypothesis relates to early-life exposures, but exposures throughout life may be important.”

The hygiene hypothesis is compelling and will hopefully be more fully researched in the years to come. In the meantime, what you do with the conflicting information is up to you. Parents (new and seasoned) with young kids can at least take heart: your home does not always need to be clean. Dog slobber on a few of the toys? Not a problem. The times you’ve “cleaned” a pacifier by popping it in your own mouth for a second? You may have lowered your child’s risk of developing asthma. Toddlers ate a handful of dirt? They’re just helping their immune system practice.

Now, this isn’t to say that all germs, bacteria, and viruses are gentle. Humanity has been at war with disease (and mostly lost) since the beginning. Some microbes are killers, so don’t romanticize our dirt-filled past too much. (And absolutely do not attend a measles party. There’s a perfect example of a challenge to immunity we could do without!)

While you may not want your child to kick up as much dust as Pigpen did in Peanuts, a little dirt won’t do any harm. And it may be good for them! You can tell them so while they hand wash the dishes after dinner.

Want to learn more about the hygiene hypothesis? Check out this 2011 Scientific American podcast with host Steve Mirsky and Johns Hopkins School of Medicine researcher Kathleen Barnes.  Or read my first article about the hygiene hypothesis, Good and Dirty.